The present invention refers to a device in impact wrenches, particularly for wheel nuts and wheel bolts, and of the type which incorporates a shaft, with a handle in one end thereof and a socket in the opposite end, whereby the shaft between its two ends is provided with a hub, about which is rotatably arranged a transverse arm, which supports weights and which is arranged to transfer impact movement to the shaft via stops arranged on the hub.
Impact wrenches of this design are earlier known in different embodiments, most of which operate well. With the kinetic force obtained when the impact arm is brought to hit against the stops it is possible easily to loosen even very tightly drawn bolts and nuts and also if they have become stuck by rust. All known impact wrenches however have a drawback in that there is a great risk that nuts and bolts may be tightened too hard or even so hard that they burst if the impact effect of the wrench is used when tightening them.